Research experiments were designed and conducted to characterize herbicide fate after broadcast or dormant-stem applications conducted along North Carolina roadsides as well as assess crop sensitivity to herbicides routinely used by the North Carolina Department of Transportation (NC DOT) for vegetation management. Results from this project suggest that all spray heads currently used by the NC DOT provide acceptable coverage in the treated spray swath. A notable difference between spray heads was observed in drift potential with drift increasing as application volume decreased.
Field research revealed Oust (active ingredient: sulfometuron) applied ≥ 6 wk prior to planting poses increased risk to corn, cotton, and tobacco compared other evaluated herbicides. Whereas with appropriate spray drift-prevention practices, all herbicides may be safely applied near soybean production fields ≥ 6 wk prior to planting.
Lastly, research evaluating dormant-stem herbicide efficacy indicate applications conducted March and April suppress maple, oak, and sweetgum growth more than applications occurring from December through February; although it should be noted application performed in March and April present increased risk to neighboring sensitive crops.
This information can be used by the NC DOT Roadside Environmental Unit to aid decision making and ensure all appropriate precautions are implemented to minimize off-target movement with respect to sprayer setup, product selection, and application timing.
